Cnideria and Ctenophora

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radiata
P. Cnidaria (formerly called the P. Coelenterata)
P. Ctenophora
gastrovascular cavity/coelenteron
extracellular digestion
polyp
medusa/medusoid
"alternation of generations“
cnidae
diploblastic
Fig. 33-7
(b) Jellies (class
Scyphozoa)
(c)
Sea wasp (class
Cubozoa)
(d) Sea anemone (class
Anthozoa)
(a) Colonial polyps (class
Hydrozoa)
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Fig. 13.2
radiata
P. Cnidaria (formerly called the P. Coelenterata)
P. Ctenophora
gastrovascular cavity/coelenteron
extracellular digestion
polyp
medusa/medusoid
"alternation of generations“
cnidae
diploblastic
Fig. 13.9 Figure 06_01
Hydra
-fresh water
-no medusa
-not colonial
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Fig. 13.3
epidermis
epitheliomuscular cell
myofibrils
interstitial cell
cnidocyte
cnidocil
nematocyst
operculum
mucus-secreting cell (especially on basal disc)
receptor/sensory cell
nerve cell/neuron (form nerve nets)
gastrodermis (mucus secreting cell, nerve cell/net,
and…)
nutritive-muscular cell
gland cell
Figure 06_03
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Figure 06_02
Fig. 13.7
Dioecious/gonochoristic with “direct”
development
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C. Hydrozoa
hydroid colony
Obelia
monopodial
sympodial
polymorphism
gastrozooid
gonozooid
Physalia
gonophore
dactylozooid
hydromedusa
velum
manubrium
planula
actinula
medusoid suppression
hydrocorals
Obelia, a
colonial hydroid
Figure 06_14 Fig. 13.9
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C. Hydrozoa
hydroid colony
Obelia
monopodial
sympodial
polymorphism
gastrozooid
gonozooid
Physalia
gonophore
dactylozooid
hydromedusa
velum
manubrium
planula
actinula
medusoid suppression
hydrocorals
Figure 06_16cont
Figure 06_15
C. Hydrozoa
hydroid colony
Obelia
monopodial
sympodial
polymorphism
gastrozooid
gonozooid
Physalia
gonophore
dactylozooid
hydromedusa
velum
manubrium
planula
actinula
medusoid suppression
hydrocorals
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Figure 06_11
planula larvae
“medusoid suppression”
hydrocorals
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Figure 06_06
Figure 06_05
C. Scyphozoa
jellyfishes
scyphomedusa
no velum
manubrium stomach gastric pouches
manubrium with oral arms
gastrovascular canals
rhopalium
statocyst
ocelli
planula scyphistoma strobila ephyrae
scyphomedusa
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Figure 06_07 Figure 06_08
Figure 06_10
Class Cubozoa, a cuboidal medusa
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Figure 06_18
C. Anthozoa
sea anemone
siphonoglyph
biradial symmetry
acrorhagi
corals
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Figure 06_20
Acrorhagi used in defense against other anemones
Figure 06_22
Figure 06_23
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Text Art 06_02
The demise of a phylum of protists: phylogeny of Myxozoa and other
parasitic cnidaria. Siddall ME, Martin DS, Bridge D, Desser SS, Cone DK
(1995)
Abstract
The notion that members of the phylum Myxozoa Grassé, 1970 do not properly belong in
classifications of protists has frequently been suggested because the infective spores of these
parasites are not unicellular. Systematists have failed to be decisive about myxozoan phylogenetic
affinities, either finding the suggestion of a cnidarian connection to be preposterous or considering
the recent suggestion of a relationship with nematodes to be an obvious failure of molecular
phylogenetics. Thus, the group has remained in classifications as a protistan phylum in its own right.
The ultrastructure of the development of myxozoans was critically re-examined in order to more
fully explore the possibility of morphological synapomorphies with metazoan taxa. These
morphological characters, in combination with small ribosomal subunit gene sequences, were used in
a phylogenetic analysis in order to assess myxozoan origins. The results unequivocally support the
inclusion of myxozoans as a clade of highly derived parasitic cnidarians, and as sister taxon to the
narcomedusan Polypodium hydriforme. Reassessment of myxozoans as metazoans reveals terminal
differentiation, typical metazoan cellular junctions, and collagen production. Their "polar capsules"
are redescribed as typical nematocysts bearing atrichous isorhiza. Insofar as taxa cannot be
contained within other taxa of equal rank, the phylum Myxozoa is abandoned and it is recommended
that the group as a whole be removed from all protistan classifications and placed in a more
comprehensive cnidarian system.
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Metazoan characteristics of the myxozoan Thelohanellus nikolskii
A. Intercellular
cytoplasmic
communication seen
between arrows.
Scale bar = 1 um
B. Septate (sj) and
desmosomal (dj)
junctions with
characteristic
tonofilaments (t)
bewteen adjacent
sporogenic cells (s).
Scale bar = 1 um
Cnidarian characteristics of the myxozoan Thelohanellus nikolskii
C. Extracellular
production of crosslinked
collagen (cf)
by a pansporoblast
(PS), arrow indicates
active exocytosis of
tropocollagen (tc).
Scale bar = 1 um
Structures seen in the development of
the so-called "polar capsule" of
Thelohanellus nikolskii labeled in
accordance with the homologous
structure in cnidarian nematocysts.
Figures A through D represent the
earliest stage in cellular ontogeny
through to that of the mature
nematocyst respectively.
c, cnidocyte; pt, preinverted tubule; np,
nematocyst primordium;
s, differentiating sporogenic cells;
th, tubular thread
Scale bar = 1 um
c, cnidocyte; np, nematocyst
primordium; it, inverted tubule;
s, differentiating sporogenic cells.
ai, atrichous izorhiza, sh, shaft of
atrichous izorhiza; op, opercular
cap of atrichous izorhiza; N,
mature nematocyst Scale bar = 1
um.
From combined morphological and 18S rDNA characters
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Text Art 06_02 Fig. 13.38
Figure 07_06
Chapter opener 07
P. Ctenophora
comb jelly
comb rows
colloblast
anal pores
apical sense organ
modified medusa?
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Figure 07_04 Figure 07_01
Figure 07_02
Table 07_01 Figure 07_05
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